Electrode for electric discharge tubes



P 1950 1 R. F. CRONERT 2,521,451

ELECTRODE FOR ELECTRIC DISCHARGE TUBES Filed Oct. 7, 1948 Patented Sept.5, 1950 Rickard Folke Cronert, Enskede, Sweden, assignor to LumalampanAktiebolag, Stockholm, Sweden, a corporation of Sweden ApplicationOctober 7, 1948, Serial No. 53,345 In Sweden March 1, 1948 2 Claims.

This invention relates to an electrode for cold cathode electricdischarge tubes.

The electrode referred to consists of a sleeve, preferably with closedbottom, the upper rim of which, facing the discharge, is covered by twothin superpositioned discs of mica or similar insulating materialprovided with centre openings for the discharge are and held in positionby fastening means. The under disc is attached to the rim fastenersprotruding from the rim and bent down over said disc, and these bentdownfasteners are covered by the upper disc, attached to the former disc bymeans of fasteners electrically separated from the first-mentioned ones.As no electrical conducting connection exists between the elementsholding the discs together and the electrode sleeve a stabilized arc iseffected and the discharge concentrated to the sleeve interior.Blackening of the tube end is avoided as no sputtering can occur fromthe rim of the sleeve. The electrode sleeve is covered on the insidewith a layer of emitting material.

The electrode according to this invention I is very simple tomanufacture and offers special advantages in connection withdegasification of the electrode, which must be carried out duringmanufacture of the discharge tube. The insulating discs which cover theupper part of the electrode, can be made so wide that they practicallyextend to the wall of the discharge tube. When degasifying theelectrode, which usually is done by heating with a high frequency coil,heating can be carried to a very high temperature. The insulating discssupport the electrode sleeve so that the latter does not come intocontact with the wall of the discharge tube and causes bursting of theenvelope.

This invention will be described in connection with an example ofconstruction as shown in the accompanying drawing forming a part hereof.Fig. 1 shows a longitudinal section through an electric discharge tubeprovided with an electrode arrangement made in accordance with thisinvention taken along the line of Fig. 3. Fig. 2 shows the upper part ofthe same electrode in a longitudinal section along line 22 of Fig. 3 andextending at a right angle to the section shown in Fig. 1. Fig. 3 is across section through the tube with the electrode arrangement seen fromabove.

The end of discharge tube 3 is closed in a known way by means of a lampstem 4, in the compressed part 5 of which two lead-in wires 6, 6 aresealed. To the upper parts of these lead- 2 in wires 6, 6 an electrodesleeve is welded in the following way. The electrode sleeve 8, whichconsists of a piece cut from an iron tube of suitable dimensions, isprovided at its lower end with a suitable cap 1. The respective lead-inwires 6 are attached to the inside of the cap collar 7 and to theadjacent part of sleeve 8 by spot welding. At the upper end of thesleeve, also by means of spot Welding, two pins '9, 9 are attached attwo diametrically opposite points. The upper edge of sleeve 8 is coveredby a mica disc l5 provided with holes [0, l0, so that the disc can bethreaded on over the pins 9, 9. After putting on the disc, the top partsII, II of the pins are bent down over mica disc I5. On top of mica discI5 is placed another mica disc M, which by means of two U-shaped clampsis secured to mica disc 15. These clamps I6, 16 are attached at twodiametrically opposite points of the edge on the discs and are, as willbe seen from Fig. 3, arranged along a line 22, which runs at a rightangle to line l-|, along which pins H, I I are attached. These clampsl6, it, which are turned towards the discharge gap, are thus by safeinsulation separated from the electrically conducting electrode parts,which are hidden by the mica discs. Mica discs 14 and I 5 are providedwith centre openings, l3 and I2 respectively, which permit the dischargeare to pass through to the interior of electrode sleeve 8. The inside ofthe electrode sleeve 8 is suitably covered with a layer of electronemitting material. The insulating discs i4 and I5 extend nearly to thewall of tube envelope 3, which permits the electrode to be supported inthe above described way by these discs during degasification.

The construction shown is only to be regarded as an example. It is notalways necessary to provide the electrode sleeve 8 with a bottom, or, ifsuch a bottom is suitable, the sleeve may be pressedin one piece withsuch a bottom. To cut the electrode sleeves from a tube, as mentionedabove, is, however, very advantageous from the viewpoint of manufacture.Instead of pins '9, 9, lugs can be punched out on the upper parts of theelectrode sleeves; and instead of the clamps [6 shown, other fasteningdevices can be used, for instance fastening by means of wire clips asused for fastening paper together by means of a paper fastener,attaching by means of riveting, etc.

What I claim is:

1. In a cold cathode electric discharge tube having a tubular envelope,an electrode comprising a metal sleeve extending axially centrally ofthe envelope adjacent to one end thereof, metal fastening elementsextending from the inner end of the sleeve, a thin disc of insulatingmaterial disposed across said end of said sleeve, said fasteningelements comprising diametrically opposed pins extending through thedisc to secure it in place, a masking disc of thin insulating materialdisposed inwardly of and. adjacent to the first mentioned disc andfastening means engaging said discs at their peripheries for securingthem together, said fastening means comprising diametrically opposedclips peripherally 01T- set from the diametral plane passing throughsaid pins and said discs extending to the vicinity of the wall of theenvelope and being provided REFERENCES CITED The following referencesare of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,984,482 Imamura Dec. 18, 19342,118,981 Muncheryan May 31, 1938 2,244,070 Kurz June 3, 1941 2,310,983Miller Feb. 16, 1943 2,375,808 Miller May 15, 1945

